OFFSET
0,4
FORMULA
EXAMPLE
G.f.: A(x) = 1 + x + x^2 + 2*x^3 + 6*x^4 + 23*x^5 + 110*x^6 + 607*x^7 +...
where, by definition,
A(x) = 1 + x/(A(x) - x) + x^2/(A(x) - 2*x)^2 + x^3/(A(x) - 3*x)^3 + x^4/(A(x) - 4*x)^4 + x^5/(A(x) - 5*x)^5 +....
Also, the g.f. satisfies:
A(x) = 1 + x/A(x) + 2*x^2/A(x)^2 + 6*x^3/A(x)^3 + 23*x^4/A(x)^4 + 104*x^5/A(x)^5 + 537*x^6/A(x)^6 +...+ A080108(n)*x^n/A(x)^n +...
PROG
(PARI) {a(n)=local(A=1+x); for(i=1, n, A=sum(m=0, n, x^m/(A-m*x+x*O(x^n))^m)); polcoeff(A, n)}
for(n=0, 30, print1(a(n), ", "))
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Apr 17 2013
STATUS
approved